This invention relates generally to push-to-talk (PTT) voice communication systems, and more specifically relates to an improved capability of such a system that allows a destination subscriber to selectively control the acceptance of incoming calls.
Push-to-talk communication systems, such as the Nextel wireless communications system in the United States, are known. Subscribers of such systems utilize a wireless mobile terminal (MT) that includes a push-to-talk button and a display that lists the names of other subscribers on a Pal list such as shown in FIG. 5. Voice communications proceed in a half-duplex mode in which only one subscriber talks, i.e. transmits, at one time while holding down the PTT button. The recipient of the voice communication is determined by the originating subscriber selecting the recipient from among a list of Pals shown on the screen of the originating subscriber's mobile terminal. It is also possible for the originating subscriber to transmit the voice communication simultaneously to a plurality of other subscribers by selecting a group Pal icon that defines a plurality of individual subscribers to receive the communication.
A call is typically initiated by the transmission of a short voice message from an originating PTT subscriber to the destination PTT subscriber. The voice message is entered by depressing the PTT button while inputting a spoken message causing a series of packets containing the spoken message to be delivered to the destination subscriber as determined by the address of the packets. The system attempts to deliver these packets to the destination subscriber's mobile terminal. The destination subscriber's mobile terminal receives the initial voice message, converts the electronic encoded voice message into an analog audio signal, and plays the voice message over the speaker of the destination subscriber's mobile terminal. A first message could be: “Hello Dan, this is John. Are you there?”
The PTT communication technique has an advantage of quickly conveying information via short bursts of voice transmissions, but suffers from privacy and interruption disadvantages. The destination subscriber may move from an environment (driving in a car) where an incoming communication would not cause a problem to another environment (entering a meeting room where a conference is in progress) where the broadcast audio from a new incoming call would create an unwanted interruption. Even if the subscriber is in an environment where an incoming call would not cause an unacceptable interruption, there is the possibility that the originating subscriber's initial voice message could be embarrassing to the destination subscriber, such as receiving, “Hey Dan, are you ready to go to the party?” while the destination subscriber (Dan) is with a client at a job site and had just told the client that he will not be able to finish the job before leaving in order to keep an important prior commitment. Although the subscriber could turn off his PTT mobile terminal, log off the PTT system, or turn down the audio volume to a near off level, these options eliminate the possibility of receiving any PTT communications. If the destination subscriber essentially mutes his audio output, an originating subscriber will not know that the destination subscriber will be unavailable since the destination subscriber's presence state as shown on the originating subscriber's Pal screen display will show the destination subscriber as logged on and available to receive calls. The failure to reach the destination subscriber may lead the originating subscriber to make incorrect assumptions e.g. they ignored me or cause undue concern e.g. why weren't they able to respond. Turning off the PTT mobile terminal or logging off will eliminate the unwanted interruptions, but requires the subscriber to have to power up the terminal and/or log into the service to restore communications.
There exists a need to provide destination PTT subscribers with a way to manage an incoming call that eliminates the uncontrolled audio broadcast of voice messages with an incoming call while still allowing the destination subscriber the flexibility of electing to accept at least some part of the incoming communication. Preferably the originating subscriber should be apprised prior to attempting the call that the destination subscriber is using incoming call management.